Substrates employed in semiconductor microelectronic and other devices are generally manufactured by a method in which a monocrystal is epitaxially grown onto a seed crystal to create an ingot, and then the ingot is sliced. Various studies have been done on ways to reduce the cost of manufacturing the substrates in situations where this manufacturing method is employed.
With the objective of reducing crystalline defects due to dislocations, Patent Document 1 discloses a method according to which a mask layer having window openings is formed onto a seed crystal (substrate), and a monocrystal is grown through the mask layer. Also given is a method of obtaining GaN single-crystal substrates by employing GaN crystal as a seed crystal, epitaxially growing a GaN monocrystal onto the GaN crystal to form an ingot, and then slicing the ingot into a plurality of wafers.
Patent Document 2, meanwhile, as a way to fabricate large-area substrates having uniformly low dislocation density, sets forth a method including a first stage of growing a Group III-V nitride material under pit-forming growth conditions, and a second stage of growing a III-V nitride material under pit-filling conditions.    Patent Document 1: Int'l. App. Pub. No. 1999/23693 (pamphlet)    Patent Document 2: Japanese Nat'l. Stage App. Pub. No. 2007-519591